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Published on: March 7, 2025
828
Pit initiation on nitinol in simulated physiological solutions.
1Exponent, 149 Commonwealth Drive, Menlo Park, California, 94025.
Summary
Inclusions initiate pitting corrosion on nitinol (nickel-titanium alloy) wires. The size of inclusions, leading to titanium depletion, is the primary factor, not the inclusion type.
Area of Science:
- Materials Science
- Corrosion Science
- Biomaterials Engineering
Background:
- Inclusions are implicated in pitting corrosion initiation on nitinol.
- The specific role and type of inclusions in nitinol pitting remain unclear.
Purpose of the Study:
- To investigate the role of inclusions in the initiation of pitting corrosion on electropolished nitinol wire.
- To determine if inclusion type is a critical factor in pit initiation.
Main Methods:
- Potentiodynamic polarization
- Scanning electron microscopy (SEM)
- Energy dispersive X-ray spectroscopy (EDS)
Main Results:
- Corrosion was limited to single primary pits on tested nitinol wires.
- Identified Ti2NiOx inclusions within primary pits.
- Secondary pits forming within primary pits indicated inclusions as initiation sites.
- Titanium depletion in the alloy matrix adjacent to inclusions provides the most viable explanation for pit initiation.
Conclusions:
- Inclusion size, influencing titanium depletion, is the key factor in nitinol pitting initiation.
- Inclusion type plays a minor, secondary role in the pitting process.
